1. Field of the Invention
The present invention relates generally to color device modeling and specifically to determining a format of samples of a color device space in order to create a color device model.
2. Description of the Related Art
Color device modeling usually entails sampling the device space and taking measurements. For a printer that uses Red, Green and Blue (RGB) as an interface (a so-called “RGB printer”), this could mean sampling the RGB space uniformly using a 9×9×9 grid, for instance, and measuring each color patch with a spectrophotometer. The use of a complete sampling grid is not strictly speaking a necessity, but it allows efficient interpolation algorithms, such as a tetrahedral interpolation algorithm, to be used later on in the device model building.
For devices with more channels, a full sampling grid may not be desirable. For a Cyan, Magenta, Yellow and blacK (CMYK) printer, a 9×9×9×9 sampling grid would mean printing and measuring 6561 patches. This is quite time consuming. It has been observed that for practical purposes, it is more efficient to use denser sampling for low blacK (K) levels and coarser sampling for high K levels. The ANSI IT8.7/3 target is designed with this in mind. The target does not contain randomly placed samples, however. There is still regularity within a particular K level, and one can indeed find a complete Look Up Table (LUT) structure on each K level.
If the layout of a target is known, it is possible to pre-determine the LUTs contained in the target, even by human inspection. In other words, if it is known the target is an IT8.7/3 target, then the K levels are known as well as the CMY LUTs on each K level.
However, a general problem exists that a sampled target may not be known when a color management system is implemented. One possible cause for this could be because a sampled target is not a standard target, which would be the case for multi-channel printer devices because the industry has not standardized on a multi-channel printer device characterization target yet. It could also be because the target only comes out after the system (e.g. software) is built. It would of course be nice for a system to support future targets. To meet this goal, hardcoding the locations of sampling points for LUTs is not desirable.
There is therefore a need to devise an adaptive method that would take a set of data points, perform analysis and determine the LUTs contained in the dataset. Various aspects of the present invention meet such a need.